What are the logs and how can they be used?
Logs are text files written by programs that record various diagnostic information about what the program is doing, what errors it encounters, and any other helpful traces that can help developers diagnose problems.
For modders, logs are an invaluable tool for troubleshooting problems with the game, as it helps to figure out what the game was trying to do and what went wrong.
Types of Minecraft logs
Minecraft has several log kinds with different uses.
Regular logs
Located in the game's logs folder, these are the logs that contain everything that happens to the game from startup to exit.
They include basic startup information, the process of booting the game and loading game assets such as resource and data packs, mods, world generation progress and errors, server connection information, chat logs. Because of its comprehensiveness, this is one of the most useful log files to consult when troubleshooting the game.
🙈 As you may have noticed, these logs contain information that may be considered sensitive, such as the folder where your game starts (which is the user folder by default), IP addresses of the servers you connect to, all chat messages, and commands.
Always review your logs before sharing them with others, and read on to learn how to share them safely with sensitive information automatically censored.
Crash reports
When a game encounters a problem that forces it to close (aka crash), it often creates an additional file called “crash report” in the crash-reports folder. These reports contain the whole summary about the environment the game is running in (like hardware, drivers and system libraries loaded), mods and of course the error itself.
Sometimes the game doesn't write the error to the regular logs at the time of the crash, or only writes part of it, so it's always worth checking the crash reports as well.
JVM crash logs
Minecraft (or more specifically the Java Edition of it) runs on the Java Virtual Machine (JVM). Some things like drivers or memory issues can cause this machine to stop working properly and exit abnormally (crash). When this happens, the game stops completely, which means it cannot log anything. In these cases, the JVM writes a file similar to the Minecraft crash report named hs_err_pidXXXXX.log (where XXXXX is the game process ID), as well as prints out the summary from it to the console output (“Live log” in Modrinth App).
JVM crash logs contain a short summary of the problem, arguments used to start the game, information about the exception (error), and a lot of information about the inner workings of the machine. This log is useful for developers of “native” mods (like Sodium). It may also give you as a user a clue as to what the problem might be.
🚫 Never share unedited JVM crash logs with anyone! These logs contain the game's startup arguments, which contain your game access token. If leaked, this token will give others full access to your Minecraft account until it expires.
Before sharing them, use your editor's search tool to find all occurrences of the --accessToken argument. Remove both it and the long string of random characters that follows it (e.g., --accessToken eyJhbG[...]nDW0I). Note that it's repeated several times in different parts of the log.
Sharing your logs
Whether you're asking for game crash support in our amazing community on Discord, in a specific mod/modloader community, or reporting a bug to a mod/modpack creator, it's always worth including any relevant logs.
However, as you've probably noticed, logs can contain some sensitive information. Also, reading logs from the plain file is not always convenient. For this reason, we recommend uploading your mods to mclo.gs, a special Minecraft log sharing service.
mclo.gs removes many types of sensitive information, is able to automatically analyze common errors, provides easy to read highlighting, and the ability to link specific parts of the log. Uploaded log files will also be removed 90 days after last viewing.
⚠️ mclo.gs currently does not support JVM crash logs and will not remove access tokens.
Here is how you upload your logs in popular launchers:
Modrinth App
Modrinth App
Regular logs
In the instances list, click your instance.
Navigate to the Logs tab.
Select the correct log file the dropdown list.
Click Share to upload it and get the URL.
Crash reports
🙁 Modrinth App doesn't currently support viewing and uploading crash reports directly from the app. You will need to upload them manually.
Open your instance's folder:
Right click your instance in the instances list. Select 📂 Open folder from the menu.
Alternatively, click on your instance and then click the 📂 Folder button.
Locate and open
crash-reportsfolder.Open mclo.gs in your browser.
Drag and drop the correct log file into the text field on mclo.gs.
Click 💾 Save.
Copy the URL from the address bar.
JVM crash logs
🙁 Modrinth App doesn't currently support viewing and uploading JVM crash logs directly from the app. You will need to upload them manually.
Open your instance's folder:
Right click your instance in the instances list. Select 📂 Open folder from the menu.
Alternatively, click on your instance and then click 📂 Folder button.
Locate the JVM crash log file (named something like
hs_err_pidXXXXX.log).⚠️ Edit it with any text editor to remove the dangerous sensitive information.
Save the edited crash log.
Open mclo.gs in your browser.
Drag and drop the edited crash log into the text box on mclo.gs.
Click the 💾 Save button.
Copy the URL from the address bar.
Prism Launcher
Prism Launcher
Regular logs
Right-click your instance in the main window.
Select Edit from the menu.
Navigate to the Other logs tab.
Using the dropdown list at the top, select the log file from the
logs/directory (for example,logs/latest.logfor the most recent log).Click Upload.
Crash reports
Similar to regular logs. From the dropdown list, select a file from the crash-reports/ folder.
JVM crash logs
Similar to regular logs. From the dropdown list, select a JVM crash log file (named something like hs_err_pidXXXXX.log).